Code Editor: Remove keeping track of `wp.codeEditor` instances since unused and no removal of instances upon deletion, leading to memory leak.

See #12423.


git-svn-id: https://develop.svn.wordpress.org/trunk@41852 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/js/code-editor.js

@@ -25,14 +25,6 @@ if ( 'undefined' === typeof window.wp.codeEditor ) {
 		onUpdateErrorNotice: function() {}
 	};
 
-	/**
-	 * All instances of code editors.
-	 *
-	 * @since 4.9.0
-	 * @type {Array.<CodeEditorInstance>}
-	 */
-	wp.codeEditor.instances = [];
-
 	/**
 	 * Configure linting.
 	 *
@@ -252,9 +244,6 @@ if ( 'undefined' === typeof window.wp.codeEditor ) {
 			codemirror: codemirror
 		};
 
-		// Keep track of the instances that have been created.
-		wp.codeEditor.instances.push( instance );
-
 		if ( codemirror.showHint ) {
 			codemirror.on( 'keyup', function( editor, event ) { // eslint-disable-line complexity
 				var shouldAutocomplete, isAlphaKey = /^[a-zA-Z]$/.test( event.key ), lineBeforeCursor, innerMode, token;